Comproportionation constant

In general, thermodynamic stability of a mixed-valence dinuclear complex, which is denoted as a combination of reduced (Red) and oxidized (Ox) sites, Red-Ox, is exhibited as a difference in redox potentials AE° = E°(Ox-Ox/Red-Ox) - °(Red-Ox/Red -Red). This difference is related to the comproportionation constant, Kc, defined in Eq. (1) ... 

In fact, when there is no interaction a statistical treatment shows that the comproportionation constant, Kcom, takes a value of 4 and, therefore, AE° = 35.6 mV. In this case the cyclic voltammogram is of... 

Its one-electron oxidation (Fe Fe ) product has a comproportionation constant of 10 and near IR absorption band with 940 = 27,000, both consistent with Robin and Day334,335 jjj valence character7 The bis-triazacyclononane ligand (142), btacn,... 

Complexes, see also specific type in solution, structures, see X-ray diffraction n-Complexes, 4 178-184 Complex formation constant, outersphere, 43 46, 55 electrovalent interaction in, 3 269-270 Compressibility coefficient of activation, 42 9 Comproportionation constants, class II mixed-valence complexes, 41 290-292 Comproportionation equilibrium, 41 280-281 Compton effect, 3 172 Conantokins, calcium binding, 46 470-471 Concanavalin A, 36 61, 46 308 Concensus motif, 47 451 Concentration-proportional titrations of poly-metalates, 19 250, 251, 254 Condensation... 

Comparison of Redox Potentials and Comproportionation Constants for Symmetrically Substituted Dinuclear Osmium and Ruthenium Complexes... 

Suppose a compound, M, is observed to undergo two successive one-electron reduction steps (equation 5). The comproportionation constant Kc for reaction (6) is simply given by expression (7). At 298 K, with °, — E°2 = A ° expressed in mV, then expression (7) reduces to Kc = exp... 

A related example54 was the decrease in the value of the comproportionation constant with increasing dielectric constant of the medium for the system [Ru(NH3)5(4,4 -bipyridyl)-Ru(NH3)5]6+,5+ 4+, which was attributed to the decrease in the electrostatic contribution to the stability of the mixed valence species as the dielectric constant increased. 

Table 6 Comproportionation Constants (Kc) and Intervalence Charge Transfer (1VCT) Bands for Mixed Valence Binuclear...

Table 11 Comproportionation Constants (Xc) and Intcrvalence Charge Transfer (IVCT) Bands for Mixed Valence Binuclear Complexes [RuXL2]2L"...

The comproportionation constantly (7) is determined by the equilibrium for class I and II complexes,... 

Ruthenium(III/II) Couples, Comproportionation Constants, and MMCT Band Properties... 

Elaborations of these basic concepts can be found in studies of the comproportionation constant of mixed-valence complexes (37, 52, 53). 

Not corrected for comproportionation constant. r No MMCT band was observed. 

COMPROPORTIONATION CONSTANTS AND MMCT BAND PROPERTIES OF SYMMETRIC... 

From the data of redox potentials given in Table 1, we can calculate the comproportionation constants of the mixed-valence state defined as follows. 

Returning now to the comproportionation equilibrium, it is interesting to notice that for large systems (2 mm co) the comproportionation constant tends towards a statistical limit of 4 (see below). Then a single electrochemical wave is observed, a fact which has frequently dissuaded researchers from further studies on such binu-clear complexes. However, even in this apparently unfavorable case, the proportion of mixed-valence species at half-oxidation (reduction) is, according to Eq. (3), a comfortable 50 %, nevertheless allowing a meaningful correction. 

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